INHIBITION OF EPIDURAL SCAR FORMATION AFTER LUMBAR LAMINECTOMY IN THERAT

Study Design, An animal model of laminectomy in rats was used to study scar tissue formation around the spinal cord, Dexamethasone, in contr olled-release form, was tested in this system for its ability to decre ase fibrous tissue formation. Objectives, The results were evaluated t o determine whether dexamethasone in a biodegradable controlled-releas e vehicle could be used to limit scar tissue formation around the spin al cord after laminectomy. Summary of Background Data. Steroids can de lay the formation of scar tissue. Continued treatment with r=s dexamet hasone results in various unacceptable side effects. Use of biodegrada ble controlled-release vehicles to deliver drugs may allow for prolong ed low-dose treatment, concentrated at the surgical site, thereby avoi ding side effects. Methods. forty-four Sprague Dawley rats underwent l aminectomies and were treated with dexamethasone in one of two control led-release vehicles or with vehicle alone. After 4 weeks, the rats we re killed and histologic sections prepared from the spines were examin ed and graded by a pathologist, In addition, the dexamethasone prepara tions were introduced into Hunt-Schilling wound chambers, which were i mplanted in rats. Four weeks after implantation, the wound chambers we re removed and the tissue inside was assayed for DNA and protein conte nt. Results, Dexamethasone acetate (Decadron, MSD, West Point, PA) sig nificantly reduced the density of the scar tissue undermining the lami nas. Steroids embedded in polymer did not change the scar formation in the back, but did decrease protein and DNA values in wound chamber ti ssues, Conclusions, Long-term release of small amounts of steroid from the polymer poly-carboxy-phenoxy-propane does not appear to reduce sc ar at laminectomy sites but does decrease the protein:DNA ratio in wou nd chambers, In contrast, Decadron does not significantly alter the bi ochemistry of wound chamber tissue but does reduce scar in the back.